Apparatus for stretch bending metal strip material



D. A. HUNTER 7 2,958,361

Nov. 1, 1960 APPARATUS FOR STRETCH BENDING METAL STRIP MATERIAL FiledMarch 1. 1957 IVE/S,

APPARATUS FOR STRETCH BENDING METAL STRIP MATERIAL Dudley AllisonHunter, Utica, Mich assignor, by mesne assignments, to H. K. PorterCompany Inc., Pittsburgh, Pa., a corporation of Delaware Filed Mar. 1,1957, Ser. No. 643,431

2 Claims. C 153-321 This invention relates generally to bending machinesand more particularly to a machine for bending light gauge stripmaterial of irregular cross sectional shapes which must be held in aform during bending.

Previous machines for bending material of the type described above, suchas the molding and trim material used on automobiles, have utilized afixed form. A strip of material to be bent is clamped at one of its endsto one end of the form and a form engaging plug is moved longitudinallyof the strip material for progressively 'moving the strip into a bentposition against the form.

The plugs are formed of bronze to facilitate their sliding movementalong the strip and each particular strip shape of course requires aseparate especially shaped plug. The plugs readily wear out during useon such a machine and, therefore, require frequent replacement.Furthermore, overbending is required in using such a machine since somesnap back of a bent strip cannot be avoided.

An object of this invention, therefore, is to provide an improvedmachine .for bending material of the above type.

A further object of this invention is to provide an improved machine forbending strip material which operates a movable form section tostretchthe material concurrently with the bending thereof so that substantiallyno overbending of the strip is required.

Another object of this invention is to provide a bending machine whichdoes not require the bronze plugs described above so that a machinerequiring a minimum of maintenance is achieved.

A further object of this invention is to provide a bending machine whichincludes a form having fixed and movable sections so that bending isreadily accomplished by clamping one end of a strip to each of thesections and then moving the movable section into a predeterminedposition relative to the fixed section.

Still a further object of this invention is to provide a bending machinefor strip material which is simple in construction, economical tomanufacture, and efiicient in operation in bending such material to apredetermined shape.

Further objects, features and advantages of this invention will becomeapparent from a consideration of the following description, the appendedclaims and the accompanying drawing in which:

Fig. 1 is a side elevational view of the bending machine of thisinvention;

Figs. 2 and 3 are transverse sectional views looking substantially alongthe lines 2-2 and 3-3, respectively, in Fig. 1; and

Fig. 4 is a fragmentary sectional view of a form section and acooperating clamp member in the bending machine of this invention.

With reference to the drawing, the bending machine of this invention,indicated generally at 10, is illustrated in Fig. 1 as including a mainsupporting frame 11 having a base 12 adapted to be floor supported.Mounted in a fixed position on the upper end of the frame 11 is a a ened Nov. 1, 1960 section 13 of a bending form 15 which determines theultimate shape of the bent strips removed from the 'ma chine 10. Asecond section 14 of the form 15 is .supported on a transverse pivot 16,carried by a support 18 arranged at one end of the frame 11, formovement of the section 14 between the dotted and solid line positionsillustrated in Fig. 1.

The form 15 is of a constant cross sectional shape to provide a supportfor a strip material during bending to thus avoid buckling or deformingof the strip. The machine 10 is illustrated in a form adapted forbending a molding strip 20 which is of a substantially C-shape intransverse section (Fig. 4). However, it is to be understood that themachine 10 is not limited to use with any particular shape molding.

The form 15 is formed with a longitudinally extended strip receivingcavity 22 which has a curved bottom surface 24'for supporting the lowerside 26 of the strip 20 and an intermediate ledge 28 for supporting theupper edge 30 of the strip 20.

The end 32 of the form section 13 remote from the section 14 is providedwith a gauge or stop 34 against which one end of a strip to be bent inthe machine 10 is initially positioned to properly locate the strip. Theend 32 also carries a clamp assembly, indicated generally at 36 mountedon a supporting structure 38 secured to and extended transversely of theform section 13, The clamp assembly 36 includes a hydraulic piston andcylinder assembly 40 having a cylinder 42 pivotally supported at 44 onan arm 46 carried by the support 38. A piston rod 48 for the assembly 40is pivotally connected at its terminal end 50 to one end of a link 52 ina toggle mechanism indicated generally at 54.

The mechanism 54 includes in addition to the link 52 which is connectedat its opposite end by a pivot 56 to an car 58 on the support 38, asecond link 60 which is connected by a pivot 61 at one of its ends tothe link 52. At its opposite end the link 60 is connected by a pivot 62to a guide bar 64 which projects through an upright slot 63 in thesupport 38 for up and down guided movement therein.

It is apparent that on extension of the piston rod 48, the togglemechanism 54 is operated to raise the bar 64. Conversely, on retractionof the piston rod 48, the toggle mechanism 54 operates to move the bar64 downwardly. On its underside, the bar 64 carries a clamp member 66which, as illustrated in Fig. 4, is of a' shape to conform to the shapeof the upper side of the strip 20. Consequently, on engagement of themember 66 with the top side of the strip 20, the strip 20 is securelyclampedbetween the form section 13 and the member 66 :and thus firmlymaintained within the cavity 22.

A similar clamp assembly 70 is carried on an upright plate 72 secured tothe end 74 of the movable form section 14 which is remote from thesection 13. The assembly 70 includes a hydraulic cylinder assembly 76having a piston rod 78 which operates a toggle mechanism 80, like themechanism 54 described in detail above, to in turn move a bar 82 up anddown in a guide slot 81 in the plate 72. The bar 82 carries a clampingmember 84 similar to the clamping member 66 previously described.

A strip 20 may thus be clamped at one of its ends to one end of the formsection 13 on operation of the assembly 36 and at its opposite end tothe remote end 74 sit" the form section 14 on operation of the clampassem A hydraulic cylinder assembly (Fig. 1) has a cylinder 91 which issupported on a pivot 92 carried by the base 12. An upwardly extendedpiston rod 94 for the assembly 90 is connected at its upper end by apivot 96 to a downwardly extended ear 98 on the end 74 of the formsection 14. On retraction of the piston rod 94 to the stop positionindicated at A in Fig. 1, the form secshown in Fig. 1. In its dottedline position, the section 14 constitutes a downwardly curved extensionof the section 13, with the ends 97 and 99 of the sections beingpositioned adjacent each other.

The specific shapes of the form sections 13 and 14 is determined by theultimate bent shape required of the strip 20. Thus, to obtain differentbent shapes of the strip 20, different curvatures are provided for theform sections 13 and 14.

In the illustrated embodiment of the invention, the section 13 is onlyslightly curved, while the curvature of the section 14 is more convex.The'pivotal support 16 for the section 14 is arranged so that when thepiston rod 94 is extended, the end 74 of the section 14 is a shorterdistance from the end 32 of the section 13 when measured along thelength of the strip 20 than when the piston rod 94 is retracted to movethe section 14 to the dotted line position illustrated in Fig. 1.Accordingly, on movement of the section 14 from its solid to its dottedline position, a strip 20 clamped to the form by the clamp assemblies 36and 70, in addition to being bent so as to conform to the shape of thesections 13 and 14, is also stretched. As a result, the bend of thestrip has a tendency to be set in the strip so that only a minimum ofspring back of the strip 20 toward its initial straight dispositiontakes place. The machine 10 is thus readily operable to quickly bend thestrip 20 to the desired shape.

The control mechanism for operating the hydraulic cylinder assemblies36, 70 and 90 is preferably centrally located so that the operator ofthe machine can handle the strips 20 and operate the cylinder assembliesfrom a single location. Since the machine does not require any partsresembling the previously used bronze plugs, a minimum of maintenance isrequired for the machine so that it can be continuously operated overlong periods of time without shut-down to thus increase the productionof which the machine is capable.

Although the invention has been described with respect to a preferredembodiment thereof, it is to be understood that it is not to be solimited, since changes can be made therein which are within the scope ofthe invention as defined by the appended claims.

What is claimed is:

1. In a machine for bending strip material to predetermined shapes, amain frame, a form for determining the final shape of the strip ofmaterial bent on said machine, said form comprising a first curved formsection mounted on said frame in fixed relation thereto and a secondcurved form section generally of substantially greater curvature thansaid first form section, means mounting said second form section on saidframe for pivotal movement relative to said first form section between astarting position and a finished position and cooperating with saidfirst section when in said finished position to provide a substantiallycontinuous form surface for supporting said strip of material, theadjacent ends of said first and second form sections being disposed inclosely spaced parallel relation when said second section is in saidfinished position, the end surface of said first form sectionintersecting the outer curved surface of said form at an acute angle andthe adjacent end surface of said second form section intersecting theouter curved surface of the form at a supplementary obtuse angle whensaid second section is in said finished position, said means mountingsaid second form section forpivotal movement about an axis beingdisposed between the ends of said second form section and inwardly ofthe curved outer surface thereof so as to avoid interference betweensaid adjacent ends during said pivotal movement, clamp means individualto said sections and mounted at the remote ends thereof for releasablyclamping said strip of material to said remote ends of said formsections, and means mounted on said frame for moving said second formsection from said starting position to said finished position, saidsecond form section being effective during pivotal movement from saidstarting position to said finished position to progressively elongatethe strip of material.

2. In a machine for stretch bending a strip of metal moulding to apredetermined shape, a main frame, a form for determining the finalshape of the strip of material bent on said machine and adapted tosupport said strip in said predetermined shape, said form comprising afirst section mounted on said frame in fixed relation thereto and havingrelatively slight curvature, a second form section generally ofsubstantially greater curvature than said first section, means mountingsaid second form section on said frame for pivotal movement relativethereto between a first position in which it co-operates with said firstform section to provide a substantially continuous curved form and asecond position in which a tangent to said second form section at theend thereof remote from said first form section is substantially tangentto said first form section at a point spaced from the end of said firstform section adjacent said second form section, a clamp mounted on saidfirst form section at said end thereof, another clamp mounted on saidsecond section at said end thereof, each of said clampscomprising a jawadapted to fit a portion of said strip and co operate with said form forholding one end of a said strip against movement relative to the form,means mounting said jaw on said form for movement toward and away fromsaid form, and means for moving said jaw toward said form to clamp oneend of a said strip to said form and hold it against movement relativethereto, said means pivotally mounting said second form section being sodisposed relative to said first form section that the distance betweensaid clamps measured along a said strip progressively increases duringmovement of said second form section from said second position to saidfirst position, and means mounted on said frame for moving said secondform section between said first and second positions, said meanspivotally mounting said second form section supporting said second formsection for pivotal movement about an axis disposed between the ends ofsaid second form section and inwardly of the curved outer surfacethereof.

References Cited in the file of this patent UNITED STATES PATENTS281,640 Mosler July 17, 1883 975,184 Walsh Nov. 8, 1910 1,710,261Kellogg Apr. 23, 1929 1,804,384 Miller May 5, 1931 2,457,483 Martin Dec.28, 1948 2,476,556 Maize July 19, 1949 2,649,129 Schlank Aug. 18, 1953

